I can’t get any country to start with them without changing them from MULTIPLYINCOME to UNCANCELLABLE in policies.csv, which always has them starting at 0.5.
I ran into a similar problem with trying to remove the regular income tax; I took all references to it out of the game except for policies.csv and removed all the effects, but it still shows up whenever I try to play.
How do I get countries to start with a MULTIPLYINCOME policy that is otherwise correctly implemented?